Swimming pools and drinking water supplies, as well as other bodies of water, must be sanitized in order to be safe for human use. As used herein, “sanitize”, and similar terminology refers to disinfecting the object by killing microorganisms.
It is instructive to review commonly available techniques that are presently used to sanitize swimming pools, drinking water supplies and other bodies of water.
In the case of swimming pools, a lack of proper sanitization can result in damaged pool equipment, damaged pool surfaces, and can allow water therein to become a breeding ground for disease-causing bacteria, viruses, parasites, algae, mold and fungi. In the case of drinking water supplies, lack of proper sanitization can result in damaged pumping equipment, damaged water holding tanks, and can allow water therein to become a breeding ground for the afore mentioned disease-causing bacteria, viruses, parasites, algae, mold and fungi. Although known methods of sanitizing swimming pools, drinking water supplies and other bodies of water have proved suitable for their intended purposes, there are nonetheless challenges inherent in the use of such methods.
In this regard, chlorine is a well-known and frequently used chemical for sanitizing both swimming pool water and drinking water. Since chlorine is an effective and relatively inexpensive sanitizing agent, and because testing for residual chlorine is inexpensive and relatively easy, chlorine is often the agent of choice for sanitizing swimming pools, as well as drinking water. Maintaining chlorine concentration of 1-3 ppm is considered adequate by many local boards of health.
In addition, use of copper/silver ions in water disinfecting techniques is also known. For example, the early Greeks used copper and silver goblets and vessels for drinking water therefrom, and for storing water. The low solubility of these copper/silver ions in the water served as a natural, controlled release mechanism that added trace amounts of these copper/silver ions into the water. The concentration amounts were high enough to purify the water without causing objectionable taste. More recent use of copper and silver ions to inactivate microorganisms in water is well-documented. In addition to being a bacteriacide, the copper and silver ions, in concentrations of parts per billion (ppb), are also effective in controlling viruses, parasites, algae, mold, and fungi.
Also, copper and silver ion disinfection of swimming pool water and drinking water has several benefits over chlorine. In this regard, copper and silver ions are chemically stable, and do not undergo the destructive reactions of aqueous chlorine, which destructive reactions can cause corrosion of metal pipes (e.g., lead and copper pipes), water pumps, pool surfaces, and other components. The corrosion, which can result from presence of chloramines, is caused by changes in chemical properties of the water. The terminology “chloramine” refers to derivatives of ammonia, and can include monochloramine (NH2CL) or a family of organic compounds. The family of organic compounds can have the formulae R2NCL and RNCL2, where R is an organic group. Other chloramines include dichloramine (NHCL2) and nitrogen trichloride (NCL3). In addition to chloramines, objectionable by-products can also include trihalomethanes (THM) and haloacetic acid (HAA). Copper and silver ions, on the other hand, do not form objectionable by-products such as chloramines, trihalomethanes (THM), and haloacetic acid (HAA).
In addition to increasing likelihood of corrosion, chloramines are also objectionable because uncontrolled amounts of chloramines can cause water quality problems, such as nitrification. Nitrification, which can result from the bacterial oxidation of ammonia, can cause loss of disinfectant residual in the water. The loss of disinfectant residual is due to conversion of ammonia into nitrite and then to nitrate. In the case of swimming pools, production of ammonia can result from sweat and urine excreted by swimmers. The sweat and urine are broken-down by chemicals in the water, such that ammonia is separated-out. Ammonia can also enter the water from decaying plant material, such as decaying leaves in the water, or from fertilizer present on nearby plants, such as fertilized grass and shrubbery located near the pool water. Presence of ammonia, in combination with chlorine in swimming pool water, can cause skin and eye irritation.
Therefore, a consideration in the art of water sanitation is the presence of chlorine in an amount that can lead to corrosion of lead and copper components (e.g., piping and pumping components) by changing chemical properties of the water. Another consideration in the art of water sanitation is the presence of chlorine in an amount that, when combined with ammonia excreted by swimmers, can lead to skin and eye irritation. Yet another consideration in the art of water sanitation is increased loss of disinfectant residual due to nitrification.
In the case of the previously mentioned trihalomethanes, the most relevant by-product is chloroform, which can escape from swimming pool water and be inhaled by swimmers. Even low concentrations of chloroform have been linked to renal and liver defects. Therefore, another consideration in the art of water sanitation is generation of trihalomethanes that can, in turn, produce chloroform.
Swimming pool owners generally take care of the chemistry of pool water in any one of several ways. For example, a swimming pool owner may hire a pool service company to apply the chemicals necessary to keep the water pH balanced and the water sanitized. In this regard, the pool service company may use various techniques for controlling the chemistry of the pool water. Those techniques may include use of the following commonly available apparatus for adjusting the amount of chlorine applied to the pool water: (1) an adjustable pump that takes liquid chlorine from a storage vat and injects it into the pool's return line; (2) a chlorine tablet holder that is installed in the water return line and that allows chlorine tablets to be dissolved at an adjustable rate; and (3) a dispenser that automatically dumps chlorine powder into a container that has pool water circulating through the container. However, another consideration in the art of water sanitation is that the initial cost and on-going maintenance costs of such commonly available apparatus may be cost-prohibitive for many pool owners.
A bromine dispenser is yet another known apparatus used for sanitizing swimming pool water and other bodies of water. In the case of swimming pools, the bromine dispenser dispenses bromine (Br) into the pool water to be sanitized. However, bromine, which is available in tablet form and can be added to pool water by a dispenser that dissolves the tablets, is more expensive than chlorine products. Also, in the case of outdoor pools, sunlight can convert active bromine into inactive bromates. In addition, bromine should not be added to swimming pool water containing chlorine because chlorine converts used-up bromine to free bromine. During this chemical conversion process, the chlorine is then converted to used-up chlorine. Therefore, another consideration in the art of pool water sanitation is that use of bromine in the presence of chlorine does not significantly enhance the process of sanitizing pool water.
Yet another method for dispensing chemicals into pool water to be sanitized is to have a pool service company bring compressed chlorine gas to the site, and inject it into the water being treated. However, this method is outlawed in many areas because of extreme hazards associated with using this method. Such hazards include possibility of pool accidents causing human exposure to the chlorine gas in a manner resulting in possible bronchial edema, asphyxiation, and pulmonary injury.
Use of ultraviolet light is yet another method for sanitizing swimming pool water. Use of ultraviolet light is preferred by some pool owners because ultraviolet light is not chemically active and does not use chemical additives. Therefore, use of ultraviolet light is more environmentally friendly compared to use of chemicals. Also, use of ultraviolet light does not require water testing, which can be inaccurate. The ultraviolet light sanitation process uses a clear glass cell containing an ultraviolet light source to sanitize the pool water. According to this method, a mercury vapor glass lamp generates shortwave ultraviolet light radiation that kills bacteria, viruses, parasites, algae, mold, and fungi. However, in order for the ultraviolet light to properly kill the bacteria, viruses, parasites, algae, mold, and fungi, the water should not be turbid or cloudy. Turbidity, which is due to suspended solids in the water, or cloudiness of the water, prevents the ultraviolet light from adequately penetrating the water in order to kill the bacteria, viruses, parasites, algae, mold, and fungi. For this reason, use of ultraviolet light can be expensive, because the water must be pre-filtered by suitable, extremely efficient filtering apparatus to remove particulate matter (i.e., suspended solids) that would otherwise cause turbidity and cloudiness. Purchase of such suitable, extremely efficient filtering apparatus increases the cost of the ultraviolet light installation. Also, use of ultraviolet light offers no residual sanitizing effect, because the sanitizing effect of the ultraviolet light will not stay in the water once the water passes by the ultraviolet light, and once the light source ceases emission of the ultraviolet light. Chlorine, on the other hand, remains in the water after treatment. Thus, a limitation or consideration associated with use of ultraviolet light is that ultraviolet light is best used in combination with chemical agents, such as chlorine, in order to suitably sanitize the water. Purchase of apparatus that uses both ultraviolet light and chlorine can increase the cost of the sanitization system.
Ozonator cells are yet another method for sanitizing swimming pool water and other bodies of water. This type of cell uses high voltage electricity to create ozone from the air. The ozone, which can be an effective bactericide, is injected into the pool water by means of a water return line connected to the pool. The ozone can be produced by a corona discharge technique that includes passing air through an electrically charged chamber that converts oxygen to ozone. However, ozone is not highly soluble in water, and therefore should be injected into the water by a compressor. Use of a compressor increases cost of using ozone. Also, when using ozone to sanitize pool water, some of the ozone may be released into the air. Such air-borne ozone may create a respiratory health hazard to pool maintenance personnel and swimmers because ozone can adversely affect the lungs. In addition, ozone leaves the water rapidly, leaves no residual, and is difficult to test, so ozone is not considered a suitable method by boards of health unless the ozone is paired with chlorine or other sanitizing agent that leaves a residual. Therefore, a consideration associated with using ozone is the initial cost of a compressor and the possible deleterious health effects.
Another method associated with swimming pool sanitization is use of inline chlorine generators. Inline chlorine generators have become accepted by pool owners in recent years. In this case, salt is added to the pool water and then an inline chlorine-generating device produces chlorine from the salt in the pool water. For the most part, known methods of on-site chlorine generation have not been adequate either for treating large commercial swimming pools, or for treating other large bodies of water. Therefore, a consideration associated with use of on-site chlorine generation alone is the difficulty of treating large commercial swimming pools or other large bodies of water.
Use of commercial chlorine products in the form of powders and tablets for treating pool water and other bodies of water is also known. These forms of chlorine usually contain cyanuric acid, which is commonly called “pool stabilizer.” Stabilizer slows down the reaction of chlorine to make the chlorine last longer in the swimming pool or other body of water. Too little stabilizer will not properly stabilize the pool water and too much stabilizer can inhibit the chlorine's ability to kill bacteria fast enough for the pool water to be safe for swimmers. Therefore, many local boards of health state that stabilizer concentration over 75 ppm (i.e., 75 parts per million) is unsafe because such a concentration will slow the ability of chlorine to kill bacteria. However, after the chlorine delivered by these products has dissipated from the pool water, the stabilizer remains. This result prevents commercial pool owners from using pill, powder, and tablet forms of chlorine as the sole method for sanitation when the pool is being used for an extended period of time due to the undesirable build-up of stabilizer during such extended periods of time. Therefore, another consideration in the art is the presence of built-up stabilizer in a concentration that slows down the reaction of chlorine to a level that presents a health hazard to swimmers.
Another issue associated with using commercial chlorine in the form of pills, powders, and tablets, and also in the form of liquid sodium hypochlorite (NaClO) or bleach, is that as much as 90% of the “chlorine” that is purchased is not chlorine, but instead includes inert ingredients that manufacturers add to their products to stabilize the chlorine, and to give it shelf life. In the case of pills, powders, and tablets, these inert ingredients can add a relatively large amount of undesirable dissolved solids into the pool water. These dissolved solids can eventually cause staining of the pool finish, discomfort for swimmers, and can shorten the life of pool filtering equipment. Therefore, another consideration in the art is presence of dissolved solids in the water due to inert ingredients added to the chlorine by manufacturers.
Another consideration relates to issues associated with transportation of chemicals used to sanitize swimming pools and other bodies of water. In this regard, chemicals used in treating pool water are manufactured off-site, usually in a rural area away from heavily populated cities and towns. Since chlorine in its pure form is a gas and is chemically unstable, additives are added to stabilize the chlorine and to give it shelf life. These additives include stabilizer, salt, calcium, soda ash, and other constituents, and are transported to the chemical manufacturing facility. After the pool chemicals are manufactured, they are placed in bottles, or other suitable containers, labeled as “hazardous products”, and then shipped to cities and towns to be stored by wholesalers in warehouses. The products are then shipped in smaller amounts to retail stores where they are purchased by service companies and end users. The chemicals are then transported to the pool site where they are stored until they are used. However, a vehicular accident while transporting concentrated pool chemicals, or improper storage of these chemicals, can result in the chemicals getting mixed with other chemicals. Mixed chemicals can cause fires, explosions, and the emission of dangerous and deadly gases that can endanger children as well as adults. Therefore, another consideration in the art is risk of injury due to transportation of such chemicals from chemical manufacturing facilities to warehouses, retail stores and end users.
Thus, in treating larger bodies of water, such as commercial swimming pools, it is difficult to achieve proper sanitation on-site using any of the above methods alone.